The ANSI/TIA/EIA-568 series of standards and their addendums and annexes, which are all fully incorporated herein and made a part hereof, describe the minimum standard for cabling installations. The original Category 5 standard from the TIA was called ANSI/TIA/EIA 568-A, and several addenda have been added to the main standard since its ratification in 1995. Category 5 Enhanced (Cat5e) is now the minimum standard for all new cabling installations, offering additional headroom over its predecessor, Category 5. The new family of cabling standards is known as ANSI/TIA/EIA 568-B. This standard currently has three sections. ANSI/TIA/EIA 568-B.1 covers the requirements of copper cabling systems, including definitions of the permanent link (different to the TIA 568-A Basic Link configuration) and channels. ANSI/TIA/EIA 568-B.2 covers copper cabling components, including cable, connectors, and patch cords. ANSI/TIA/EIA 568-B.3 covers fiber optic cabling systems and components. The performance criteria specified within the new Cat5e standard exceeds Category 5, though it remains a 100 MHz standard.
The main differences between Category 5 and Category 5e can be found in the specifications. The performance requirements have been raised slightly in the new standard. Cat5e has stricter specifications for Power Sum Equal-Level Far-End Crosstalk (PS-ELFEXT), Near-End Crosstalk (NEXT), Attenuation, and Return Loss (RL) than those for Category 5. Like Cat5, Cat5e is a 100-MHz standard, but it has the capacity to handle bandwidth superior to that of Cat5. Near-End Crosstalk (NEXT) occurs in wires packed together within a cable when portions of the signals launched on wires at one end of the cable leak into other wires at the same end, potentially disturbing the weaker signals received on those wires from the opposite end of the cable. Power Sum NEXT (PS-NEXT) is the sum of the NEXT power coupled to a wire pair from all other adjacent pairs. ELFEXT is a test parameter used when testing Category 5E UTP (unshielded twisted-pair), FTP (foil screen twisted-pair) or ScTP (screened twisted-pair) Permanent Links or channels. ELFEXT is the crosstalk from a signal transmitted on a pair at one end of the cable, measured on another disturbed pair at the opposite end from which the disturbing signal is transmitted, normalized by the attenuation contribution of the cable or cabling. The larger the value of ELFEXT loss in dB, the better the performance. PS-ELFEXT is the composite sum of all of the ELFEXT signals.
Table I compares the twisted-pair specifications of Cat5 and Cat5e.
TABLE IParameterCAT5CAT5eFrequency100 MHz100 MHzAttenuation (min. at 100 MHz)22 dB22 dBCharacteristic Impedance100 ohms +/− 15%100 ohms +/−15%NEXT (min. at 100 MHz)32.3 dB35.3 dBPS-NEXT (min. at 100 MHz)(no specification)32.3 dBELFEXT (min. at 100 MHz)(no specification)23.8 dBPS-ELFEXT (min. at 100 MHz)(no specification)20.8 dBReturn Loss (min. at 100 MHz)16 dB20.1 dBDelay Skew (max. per 100 m)(no specification)45 ns
As described above, Cat 5e cable is an enhanced version of Cat 5 for use with 1000BASE-T (gigabit) networks, or for long-distance 100 Base-T links (350 m, compared with 100 m for Cat 5). Because of the longer distances associated with Cat5e, it is advantageous to be able to connect Cat5e-rated cables together while still maintaining compliance with the standard. One way to do this is through a patch panel that meets the Cat5e standards.